The effect of landscape features on deposition to Hunter Mountain, Catskill Mountains, New York

Atmospheric deposition to montane ecosystems is higher than to adjacent low lands. However, because of the heterogeneity of mountainous landscapes, rat es of deposition are likely to vary considerably across major landscape fea tures. Estimates of total atmospheric deposition for montane areas in the U nited States are wide ranging and usually based on models that do not take into account landscape heterogeneity. Thus, little is known about the spati al variability of atmospheric deposition to these high-elevation ecosystems . We identified four landscape features that are likely to control patterns a nd rates of atmospheric deposition in mountainous terrain, including (1) fo rest edges or gaps, (2) elevation, (3) aspect, and (4) vegetation type, and we measured patterns of atmospheric deposition across them in the Catskill Mountains of New York State. We measured lead amount in the forest floor a s an index of atmospheric deposition, used these data to estimate relative deposition to the Hunter Mountain massif, and with a geographic information system (GIS) database, scaled up atmospheric deposition estimates to the H unter Mountain landscape. Area-weighted mean deposition to the region above 1000 m thigh-elevation) w as 13-43% greater than to a nearby, low-elevation site, depending upon how edges were defined. In addition, we identified "hotspots" of deposition, su ch as high-elevation, coniferous forest edge zones, where atmospheric depos ition of pollutants and nutrients was 300% greater (44 kg N . ha(-1).yr(-1) and 46 kg S.ha(-1).yr(-1)) than to low-elevation forests (11.1 kg N.ha(-1) .yr(-1) and 11.6 kg S.ha(-1).yr(-1)). Our data suggest that estimates of atmospheric deposition to mountainous te rrain that do not include landscape heterogeneity may be inadequate. Furthe rmore, current models of atmospheric deposition cannot predict "hotspot" re gions of extremely high deposition. Landscape features such as forest edges , elevation, aspect, and vegetation type should be considered in future mod eling efforts.